Position - lat / lon
Don't geocode your street address. A geocoder's pin for an address can sit 100-200 m from
where you actually are, and at a few hundred metres' landmark range that alone can swing the
solved heading by 15-20°.
- Google Maps, desktop: right-click the exact spot - the coordinates are the top item
in the menu; click to copy them.
- Google Maps, phone: long-press the exact spot to drop a pin, then tap the pin.
Elevation - metres above sea level
elev = ground elevation + (floor - 1) × floor height + camera height above the floor
- Ground elevation: any free lookup (search "elevation api" or "USGS elevation lookup") with
your lat/lon.
- Floor height: ~3.5-4 m per storey is a reasonable estimate for an office building.
- Camera height above the floor: ~1-1.5 m for a desk or window-sill mount.
Tilt & roll - degrees
Use your phone's built-in bubble level rather than any manual math:
- iPhone: Measure app → Level.
- Android: often under Camera → Pro mode, or any free "bubble level" app.
Hold the level flush against the same face the lens is on (or against the mount, if the phone
sits in a fixed cradle), pointed the same way as the camera. Tilt is degrees above horizontal;
roll is the side-to-side lean.
Heading - compass bearing the camera faces
Do not trust a phone compass indoors, especially near a steel-framed building.
Errors of 15-25° are common, and they are not a fixed offset you can just subtract - they change
depending on which way the phone is pointed.
- Best: the Calibrate button. Once a real aircraft is visible in your frame, click it
in the Overhead list on /sky, press Calibrate on
locked, then click it where it actually is in the video. This solves heading (and refines
tilt) directly from a known aircraft's real position - no external math needed.
- If no aircraft is visible yet: pick a fixed landmark in frame you can identify on a
map, look up its exact coordinates, and compute the true bearing to it from your position with
any "bearing between two coordinates" calculator. Then nudge the Heading slider on
/sky until that landmark sits at the correct spot in frame -
the az/el grid overlay helps line it up.
Horizontal field of view - degrees
Hardest one to get without opening the phone up.
- From camera specs, if you can find them:
H-FOV = 2 × atan(sensor_width / (2 × focal_length)), using the width of whatever
the streaming app actually crops the sensor to - rarely published, so treat this as a rough
starting point.
- Empirically, more reliable: with two landmarks (or two aircraft) visible at once
whose true bearing separation you know, adjust the H-FOV slider until they land that same
angular distance apart on screen.
A stated "diagonal FOV" from a spec sheet is always wider than the horizontal FOV - don't use
it directly.
Saving what you find
Heading / tilt / roll / H-FOV can be written to the server with the Save rig button on
/sky - that page deliberately never saves lat / lon / elev,
since /api/observer is a public endpoint. Keep your coordinates only in the URLs
below, or in this generator.